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    Electric Field-Induced Strain Behavior in Lithium- and Copper-Added Potassium Sodium Niobate Piezoceramics and 1-3 Piezocomposites
    (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2011) Alkoy, Ebru Mensur; Berksoy, Ayse; Tekdas, A. Serkan
    Potassium sodium niobate (KNN)-based lead-free materials were prepared and their field-induced strain behaviors were investigated. Ceramic lead-free piezoelectric materials were prepared in bulk and fiber forms with 1 mol% CuO-added potassium sodium niobate K(0.5)Na(0.5)NbO(3) and x = 7 mol% lithium-modified (K(0.5-x/2) Na(0.5-x/2)Li(x))NbO(3) compositions. Fibers were drawn using a novel alginate gelation technique. Piezocomposites were prepared from these fibers with 1-3 connectivity and an epoxy matrix. A fully recoverable electrostrain of up to approximately 0.11% was observed in the CuO-added sample, whereas the Li-modified sample yielded up to 0.10% at 50 kV/cm electric field. A strain value of up to approximately 0.03% at 50 kV/cm electric field was obtained for piezocomposites prepared from lithium-modified fibers. The high-field converse piezoelectric coefficient was calculated from the strain-electric field (x-E) graph for all samples. Strain characteristics of the bulk and piezocomposite samples were analyzed based on the variation of strain with respect to square of the polarization (x-P(2)) to determine the electrostrictive contribution to the strain.
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    Electrical Properties of 1-3 Piezocomposites with Potassium Sodium Niobate Fibers
    (TAYLOR & FRANCIS LTD, 2011) Alkoy, Ebru Mensur; Tekdas, A. Serkan; Berksoy, Ayse
    Lead-free 1 mole% CuO-added potassium sodium niobate K0.5Na0.5NbO3 (KNN) fibers were drawn using a novel alginate gelation technique. Piezocomposites with 1-3 connectivity were prepared with an epoxy matrix with various fiber volume fractions (V-f). The dielectric constant of the piezocomposites were found to increase from 67 to 190 with the addition of CuO into KNN and increasing Vf in the 1-3 piezocomposite. A fully recoverable electrostrain of 0.023% for the piezocomposites with V-f = 0.63 under an electric field of 4 kV/mm. A very high electrostrictive Q(33) coefficient of 162x10(-3) m(4)/C-2 was obtained from piezocomposites.